The simplest antilocking apparatus of this type is the so-called circulating type antilocking apparatus as described in U.S. Pat. No. 3,549,212.
Present FIG. 7 shows a hydraulic circuit diagram of a well-known circulating type antilocking apparatus. An inlet valve 4 is provided in a fluid path between a master cylinder 2, and a wheel brake 3. The master cylinder converts operating physical force applied to a brake pedal 1 into fluid pressure. An outlet valve 5 can discharge working fluid from a fluid path portion connecting the inlet valve 4 with the wheel brake 3. The working fluid discharged through the outlet valve 5 is temporarily stored in a damping reservoir 6. A pump 7 draws the working fluid thus stored in the damping reservoir 6, to deliver the same into a fluid path portion connecting the master cylinder 2 with the inlet valve 4. A check valve 8 allows only a unidirectional flow of the fluid.
In this well-known antilocking apparatus, the working fluid temporarily stored in the damping reservoir 6 and drawn by the pump 7 is forced toward the master cylinder 2. thus, the brake pedal 1 is pushed back against the driver's pedal force. This is the so-called kick-back against the brake pedal 1, which causes an undesirable pedal feeling.
Some proposals have been made in order to solve the aforementioned problem. One of such proposals is disclosed in U.S. Pat. No. 4,453,782 disclosing an antilocking apparatus. FIG. 8 is a hydraulic circuit diagram showing that apparatus.
In the antilocking apparatus shown in FIG. 8, a differential pressure responsive valve 9 and a high-pressure accumulator 10 are added to the structure of FIG. 7. The differential pressure responsive valve 9 is provided between a master cylinder 2 and an inlet valve 4. Working fluid discharged from a pump 7 is introduced into a fluid path portion provided between the differential pressure conscious valve 9 and the inlet valve 4. Thus, the working fluid discharged from the pump 7 can be prevented from flowing back to the master cylinder 2, by the interposition of the differential pressure responsive valve 9. The working fluid thus discharged from the pump 7 and prevented to flow back to the master cylinder 2 is stored in a high-pressure accumulator 10.
The problem of kick-back against the brake pedal is thus solved by the antilocking apparatus shown in FIG. 8. However, this apparatus is disadvantageous in weight, space and cost due to the high-pressure accumulator 10, which requires a back-up spring which is extremely larger in size than that of the low pressure damping reservoir 6, although the working fluid storage volume of the former is identical to that of the latter.